The literature describes the formation of nanoparticles in various classical polymers, such as organization and immobilization of metal compounds in linear, branched and crosslinked polymers. In particular, the literature describes immobilization of metals, metal ions, and metal sulfides using ionomers, and block copolymers.
Rules of complex formation are well known in physical chemistry as a consequence of more than fifty years of extensive research. Formation of such complexes may occur on the surface of dendritic polymers or in their interior. These phenomena have been described in many publications.
Preparation and analysis, physics and chemistry of nanosized materials is described for instance in the series of books of Kluver Academics On The Physics and Chemistry Of Materials With Low-Dimension Structures, such as “Physics and Chemistry Of Metal Cluster Compounds” edited by L. J. De Jongh, Kluver Academic, Dordrecht/Boston/London, 1994, and references thereof. A general drawback of the presently used methods of preparing nanosized materials is that they either require sophisticated and expensive instrumentation or tedious and extensive preparation and purification processes. Simple preparation of transiently stabilized nanosized materials in solution is possible by employing a combination of small organic ligands and amphophilic molecules. However, these clusters lack long-term stability. Also, a general disadvantage with known methods of preparing nanosized materials is that the size and size distribution of the resulting nanoparticles obey statistical rules. As a result, preparation of nanoparticles with a narrow size distribution requires tedious purification procedures.
J. U. Yue et al. have reported, in J. Am. Chem. Soc. 1993, 115, 4409–4410, a technique for preparing nanosized materials involving synthesis of zinc fluoride in poly(2,3-trans-bis-tert-butylanildimethyl-norborn-5-ene) domains within polymethyltetracyclododecene matrices, and interconversion of the zinc fluoride clusters to zinc sulfide. Yue et al. concluded that the disclosed method demonstrated a general approach for carrying out a chemical reaction within a nanoscale region of a block copolymer, and speculated that different kinds of clusters can be synthesized from a given starting material. Yue et al. hypothesized that lead sulfide and cadmium sulfide clusters can be prepared using the general approach disclosed, and reported that this same approach has been used to generate zinc sulfide quantum clusters which are superior in quality to zinc sulfide clusters generated using other techniques.
Martin Moller reported in Synthetic Metals, 1991, 41–43, 1159–1162, the synthesis of nanosized inorganic crystallites or clusters of cadmium sulfide, cobalt sulfide, nickel sulfide and zinc sulfide prepared from functionalized diblock copolymers of polystyrene and poly-2-vinylpyridine. The diblock copolymers were prepared with narrow molecular weight distributions by sequential anionic polymerization. Films were prepared by solvent evaporation with metal salts of copper, cadmium, cobalt, nickel, zinc and silver. The films were subsequently treated with gaseous hydrogen sulfide to form the corresponding metal sulfides.
W. Mahler, in Inorganic Chemistry, 1988, 27(3), 435–436, reported the preparation of polymer-trapped semiconductor particles by milling an ethylene-methacrylic acid copolymer with a metal acetate or acetylacetonate at an elevated temperature (160° C.) to form a neutralized ionomer.
T. Douglas et al. have reported in Science, Jul. 7, 1995 Vol. 269, 54–57, the synthesis of amorphous iron sulfide minerals containing either 500 or 3000 iron atoms in each cluster. The synthesis was achieved within the nanodimensional cavity of horse spleen ferritin. The report indicates that the reaction of acidic (pH 5.4) sulfide solutions within ferritin results in the in situ nanoscale synthesis of protein encapsulated iron sulfides. Douglas et al. speculated that such bioinorganic nanoparticles might be useful as biological sensors and markers, drug carriers, and diagnostic and radioactive agents. More specifically, magnetoferritin has shown potential as a contrast agent for magnetic resonance imaging of tissue and uranium oxide-loaded ferritin could have use in neutron-capture therapy. Douglas et al. have also suggested that nanodimensional metal sulfides could be useful in the preparation of semiconductors which could be of technological, and perhaps biological importance.
Y. Wang et al. have reported in J. Chem. Phys., 1987 87(12), 7315–7322, December 15, the preparation of nanodimensional lead sulfide clusters in ethylene-methacrylic acid copolymers by exchanging Pb2+ into the polymer film and then reacting the resulting lead-resin complex with hydrogen sulfide.
J. P. Kuczynski et al. have reported in J. Phys. Chem., 1984, 88, 980–984, the synthesis of cadmium sulfide in a Nafion polymer film. Small cadmium sulfide crystalline particles were reported to exhibit properties similar to those of cadmium sulfide single crystals.
M. Krishnan et al. have reported in J. Am. Chem. Soc., 1983, 105, No. 23, 7002–7003, a method of incorporating a dispersed semiconductor (CdS) throughout an ionically conductive polymer membrane (Nafion), in which a suitable redox couple and catalyst can be added to promote photocatalytic reactions on the membranes. The pre-treated membrane was immersed in a solution of Cd2+ (pH=1) to incorporate Cd2+ in the membrane by ion exchange. Subsequent exposure of the membrane to hydrogen sulfide produced spherical cadmium sulfide particles of a diameter of one micrometer or smaller. A cationic redox agent, such as methylviologen (MV2+), can be incorporated into the membrane. Kishnan et al. also reported that platinum can be incorporated into the CdS/MV2+ membrane system, and have speculated that by employing an analogous technique, incorporation of other semiconductors, such as titanium oxide and zinc sulfide, should be possible.
Albert W-H Mau et al. have reported in J. Am. Chem. Soc., 1984, 106, No. 22, 6335–6542, that hydrogen-production efficiencies from water in photocatalytic reactions at cadmium sulfide crystallites embedded in a polymer (Nafion) matrix containing a hydrogen evolution catalyst (Pt) were greater than those observed with unsupported colloidal or powdered semiconductors under similar conditions.
Y. Ng Cheong Chan et al. have reported, in Chem. Mater. 1992, 4, 885–894, methods for forming metal clusters that are less than 100 Angstroms in diameter, that have a narrow size distribution, and that are dispersed evenly throughout a nonconductive polymer matrix. These methods involve reduction of metal complexes and aggregation of metal atoms in the solid state, either in an organometallic homopolymer or in an organometallic block of a microphase-separated diblock copolymer. Chan et al. suggest that such compositions might exhibit discernable catalytic properties.
In J. Am. Chem Soc. 1992, 114, 7295–7296, Chan et al. reported the synthesis of single silver nanoclusters evenly dispersed within spherical microdomains of block copolymer films.
Sung Soon Im et al. reported, in J. Appl. Polym. Sci., 1992, 45, 827–836, the preparation of metallic sulfide and polyacrylonitril (PAN) film composites which exhibit improved electrical conductivity. The composites were prepared by a chelating method in which PAN films were treated with ammonium hydroxide solution to induce amidoxime groups which were coordinated with Cu2+ and Cd2+ absorbed to the amidoximated PAN films and subsequently treated with hydrogen sulfide gas to form CuS-PAN and CdS-PAN composite films.
M. Francesca Ottaviani et al. reported in J. Am. Chem. Soc. 1994, 116, 661–671, the preparation and characterization of Cu2+ complexes formed with anionic polyamidoamine (PAMAM) Starburst® dendrimers (SBDs). The PAMAM SBDs (generations 0.5–7.5) were subjected to hydrolysis of methyl ester-terminated generations with stoichiometric amounts of sodium hydroxide in methanol to form sodium carboxylate terminated PAMAM SBDs. The carboxylated PAMAM SBDs were treated with aqueous Cu(NO3)2 solutions to obtain SBD/Cu(II) complexes. Ottaviani et al. identified three different complexes of copper using electron paramagnetic resonance technique, including carboxylate complexes at low pH, Cu(II)-N2O2 complexes involving interactions with nitrogen centers in the internal permeable structure of the dendrimers at intermediate pH, and Cu(II)-N3O or Cu(II)-N4 complexes involving a wide number of internal sites at both higher pH and higher generation.
In J. Phys. Chem. 1996, 100, 11033–11042, Ottaviani et al. disclosed the preparation and characterization of PAMAM-SBDs/Mn(II) complexes. Ottaviani et al. concluded that Mn(II) does not interact with amino-terminated full generation PAMAM-SBDs, and only interacts probably at the second solvation shell, with surface carboxylate groups of carboxylated half generation PAMAM-SBDs.
In J. Phys. Chem. B., 1997, 101, 158–166, Ottaviani et al. disclosed the preparation and characterization of PAMAM-SBDs/Cu(II) complexes. Ottaviani et al. concluded that Cu(II) does interact with amino-terminated full generation PAMAM-SBDs as a function of pH. Three different complexes were found in the amino-terminated PAMAM-SBDs, including Cu(II)-N2O2 complexes involving interactions with nitrogen centers in the internal permeable structure of the dendrimers at intermediate pH, Cu(II)-N3O complexes and Cu(II)-N4 complexes.
In Polym. Prepr., ACS Div. Polym. Chem. 1995, 36, 239–240 Wege et al. reported the formation of polymer hybrids when methyl acrylate and vinyl acetate polymerization was initiated by radical initiators in the presence of PAMAM dendrimers. Depending on reaction conditions, both water soluble and insoluble hybrids formed. The drawback of such a process is, that the method is limited to radically polymerizable organic monomers, and, the reaction results in inseparable polymeric hybrid networks because of the chain-transfer to dendrimer that results in covalent bonds between the growing polymeric chain and the functional groups of the host, thereby irreversibly eliminating the container-properties of the dendrimers used.
In Eur. Pat. Appl. 95201373.8 (Publ. 0,684,044 A2), Meijer et al. disclosed a composition consisting of a dendrimer and an active substance. This composition is formed by mixing a dendrimer with a previously synthesized compound and treating the surface of the dendrimer with a blocking agent which is sterically of sufficient size, which readily enters into a chemical bond with the terminal groups of a dendrimer, and which can also be split off from the dendrimer thereby controlling the release of partly or fully occluded compounds. The drawback of such a process is that it is limited to the inclusion of pre-existing compounds. Another drawback is, that the method is limited to dendrimers having identical and modifiable surface groups.
In U.S. Pat. No. 5,422,379, Newkome et al. disclose the construction of unimolecular micelles that are able to reversibly expand and contract as a response to a change in the environment. These unimolecular micelles may have different structures and active reaction sites which may complex metals.